The Concha 31 occurrence is located approximately 10.5 kilometres north of Thutade Lake and 6.5 kilometres southeast of Drybrough Peak. The prospect crops out on the east side of the Finlay River in the Omineca-Cassiar mountains about 275 kilometres north of the community of Smithers.

The prospect is at the southern end of the Toodoggone Gold Camp which lies within the eastern margin of the Intermontane Belt and is underlain by a northwest-trending belt of Paleozoic to Tertiary sediments, volcanics and intrusions. The prospect is situated within a Mesozoic volcanic arc assemblage bounded to the east by the Omineca Belt and to the west and southwest by the Sustut and Bowser basins.

Permian Asitka Group crystalline limestones are the oldest rocks exposed in the region. They are commonly in thrust contact with Upper Triassic Stuhini Group andesite flows and pyroclastic rocks. These Stuhini rocks have been intruded by plutons and other bodies of the mainly granodiorite to quartz monzonite Early Jurassic Black Lake Suite and are in turn unconformably overlain by or faulted against Lower Jurassic calcalkaline volcanics of the Toodoggone Formation (Hazelton Group).

The dominant structures in the area are steeply dipping faults which define a prominent regional northwest structural fabric trending 140 to 170 degrees. In turn, high angle northeast-striking faults (approximately 060 degrees) appear to truncate and displace northwest-striking faults. Collectively these faults form a boundary for variably rotated and tilted blocks underlain by monoclinal strata.

Stuhini Group dark green andesitic lapilli tuffs with trace pyrite and locally thin bedded andesitic tuffs, striking 120 to 135 degrees and dipping 73 to 82 degrees north, underlie the Concha 31 prospect. Stuhini volcanics are variably chlorite and epidote altered. The contact between the Stuhini Group volcanics and the Toodoggone Formation volcanics lies less than 1 kilometre to the east. Toodoggone volcanics consist of crystal ash tuffs and flows with lesser agglomerates. Granodiorite of the Black Lake stock lies less than 1 kilometre to the west.

Massive chalcopyrite and pyrite occur within a quartz gangue over a 1 metre width. The zone strikes 093 degrees and dips 22 degrees to the south. Mineralized outcrop can be traced for 50 metres along strike where it disappears into the west bank of the Finlay River and under overburden to the southeast.

In 1987, two rock samples were taken from this mineralized zone. The better of the two samples yielded assay values of 92.9 grams per tonne silver, 0.58 gram per tonne gold, 0.6579 per cent copper, 0.0798 per cent zinc and 0.0584 per cent lead (Assessment Report 17459).

The Concha 1 to 6 claims were staked in the fall of 1987 on behalf of Skylark Resources Ltd. to cover the Finlay River valley. Bedrock exposure in this area is generally poor except along the Finlay River and tributaries draining into it. Samples 6801 to 6804 and 10507 to 10511 were taken from the east bank of the Finlay River on the Concha 3 claim.